Flow visualization & extrudate swell behavior of natural rubber compound in annular die capillary rheometer

This research aims to study the flow pattern and extrudate swell properties of a Natural Rubber (NR) compound in a constant shear rate capillary rheometer, using two types of annular die: convergent annular and divergent annular. Results revealed that flow patterns that occurred in the barrels of both types of annular dies were significantly different, especially the vortex flow at the barrel wall and at the die entrance. This difference in flow pattern significantly affected both diameter swell and thickness swell of the NR compound. It was also found that thickness swell was higher than diameter swell in every test condition. This difference could be explained by analysis of the complex flow pattern at the die entrance.